This invention relates in general to cellular material and more particularly to a process for forming a cellular material which is backed by a fabric material.
Foamed or cellular material which is backed by fabric is used quite extensively in the manufacture of automobile seats, its primary advantage being that the fabric backing provides a base to which upholstery material may be stitched or otherwise attached. For example, the cellular material in the seat is normally presented forwardly toward the occupant of the seat and has its forward surface covered with a suitable upholstery material which is drawn rearwardly along the sides of the cellular cushioning material and stitched to the fabric backing which normally projects beyond the cellular material in the form of a lip. Also, when the seat is provided with tufts, more stitching is normally made through the upholstery material and backing material at the creases between adjacent tufts.
For years cushions for seating have been die cut from slab foam which is obtained from a continuous casting operation and has a fabric backing attached to it with an adhesive. Once cut, the fabric-backed cushion usually undergoes skiving and slotting operations to provide it with the desired shape. These operations results in substantial waste and require considerable labor. Consequently, they are expensive. Furthermore, the shapes one can obtain from such operations are normally limited to parallel grooves, radii, and the like, since to obtain even a limited measure of efficiency, the cellular cushion or the slab from which it is cut must pass along a conveyor as the various shapes are cut into it. In other words, the shapes will correspond in direction to the direction in which the cushion or slab is advanced on the processing conveyor as the shapes are cut into it. Moreover, the lip, being pure fabric, is quite limp and therefore is difficult to position for sewing and other operations.
Intricate configurations may be created by molding the cellular material to the desired shape in a closed mold. However, all attempts by applicant to mold the cellular material against the fabric left the interstices of the fabric backing filled with a layer of cellular material of considerably greater density than the remainder of the material. This high density layer existed on both sides of the fabric since the foam material actually penetrated the fabric upon foaming against it. As a result the fabric-backed foam material was difficult to slide across sewing and other handling tables.
To increase the rigidity of the lip applicant attempted to mold a thin layer of foam contemporaneously with the molding of the major portion of the cushioning material. However, the foam material densified in the thin portion of the mold cavity, rendering the lip extremely difficult to pierce with sewing maching needles.
Also the dense layer of foam at the lip did not meet flame retardant requirements, even when large amounts of flame retardants were incorporated into the foam. In this regard the dense foam of relatively thin cross section tends to burn quite readily with the fabric acting as a wick.
Finally it should be noted that the dense foam of the lip will not absorb enough liquid palstisol to enable a vinyl cover to be heat sealed to the lip, thus leaving stitching as the only method of securing the upholstery, but stitching is, as previously mentioned, a difficult procedure due to the high friction which develops between the sewing machine needles and the high density foam.